Gene‐expression profile and localization of Na⁺/K⁺‐ATPase in rat enamel organ cells

Abstract

The sodium pump Na+/K+-ATPase, expressed in virtually all cells of higher organisms, is involved in establishing a resting membrane potential and in creating a sodium gradient to facilitate a number of membrane-associated transport activities. Na+/K+-ATPase is an oligomer of α, β, and γ subunits. Four unique genes encode each of the α and β subunits. In dental enamel cells, the spatiotemporal expression of Na+/K+-ATPase is poorly characterized. Using the rat incisor as a model, this study provides a comprehensive expression profile of all four α and all four β Na+/K+-ATPase subunits throughout all stages of amelogenesis. Real-time PCR, western blot analysis, and immunolocalization revealed that α1, β1, and β3 are expressed in the enamel organ and that all three are most highly expressed during late-maturation-stage amelogenesis. Expression of β3 was significantly higher than expression of β1, suggesting that the dominant Na+/K+-ATPase consists of an α1β3 dimer. Localization of α1, β1, and β3 subunits in ameloblasts was primarily to the cytoplasm and occasionally along the basolateral membranes. Weaker expression was also noted in papillary layer cells during early maturation. Our data support that Na+/K+-ATPase is functional in maturation-stage ameloblasts.

Localization of nucleoside transporters in rat epididymis

“…Figure shows the localization for Ent1 (A), Ent2 (B), Cnt2 (C), and sodium/potassium ATPase (Na + /K + ATPase) (D) in rat epididymis. The Na + /K + ATPase serves as a basolateral membrane marker to demonstrate the staining pattern for basolateral localization in epithelial cells . The brown staining indicates positive expression for the transporter.…”

“…The Na + /K + ATPase serves as a basolateral membrane marker to demonstrate the staining pattern for basolateral localization in epithelial cells. [17] The brown staining indicates positive expression for the transporter. Since the gap junctions, which differentiate between the apical and basolateral membranes, are near the luminal side of the epithelium, the basolateral membrane staining is a characteristic U shape (due to staining both the basal and the lateral portions of the cell) when viewing a cross-section of the tubule, which can be seen in panel D. [18,19]…”

NBCe1 (SLC4A4) a potential pH regulator in enamel organ cells during enamel development in the mouse

“…Conceivably, the low intracellular Na+ that this cotransport needs is accomplished by the activity of Na + , K + -ATPase in plasma membranes of the papillary layer (Garant and Sasaki 1986; Josephsen et al 2010; Wen et al 2014,) continuously pumping out 3Na + and importing 2 K + . In addition, other, yet unknown mechanisms must be operate in enamel organ cells to compensate for charge differences that result from increased negative charge when NBCe1 and Na + -K + exchangers are functional.…”

Enamel: Molecular identity of its transepithelial ion transport system

“…NCX removes 1Ca 2+ in exchange for 3Na + whereas NCKX exchanges 1K + and 1Ca 2+ for 4Na + . The better known Na + -K + -ATPases are also expressed largely in the cytosolic compartment of late maturation-stage ameloblasts [67]. Other proteins associated with Na + transport are discussed below.…”